mistakably

The other solution, which I've mentioned before, is that Larson and Pierre never appeared in the Rome adventure, and were wrongly ‘chronicled’ by Lara's professor-friend, instead of two rivals who just so happened to have very mistakeably similar names.

Origin

Late Middle English (as a verb): from Old Norsemistaka 'take in error', probably influenced in sense by Old Frenchmesprendre.